1990 Pontiac Bonneville back fires!!

[uaetwins]

Hello everyone,

my ponitac bonneville 1990 back fires!...i have no idea why is tht... wht are the possible reasons? below is the car detail:

VIN: 1G2HZ51C1L1238845

Year/Make/Model: 1990 PONTIAC BONNEVILLE SE

Body Style: Sedan 4 DR

Engine Type: 3.8L V6 SEFI

Manufactured In: UNITED STATES

any help will be greatly appreciated
thanks,
twins

[LMP]

If it backfires when you suddenly depress the throttle for acceleration, then this means a lean mixture condition and it traces most probably to throttle position sensor (TPS) whose purpose is exactly what the old acceleration pump was for on carburators. For steady condition, the Mass Air FLow sensor is used for proper metering.
Was this car OBD equipped in '90? ANyway, a good description of TPS flaws can be read here:
www.avigex.ca/xport/dtc21.jpg
www.avigex.ca/xport/dtc22.jpg

If backfires happen in condition other that one described above, then give more details...a burnt exhaust valve would also cause this at any speed and condition, but personnally I have not seen that in decades. It could be low fuel pressure, but that is easily tested and do test pressure first before any intrusion in fuel pump cause it is blamed much too often, too easy a culprit .

[uaetwins]

thanx a tonne for ur reply!!...i m not sure if the car is OBD compliant but i will check n get back to u...i did not get a chance to look at it today (friday)...hopefully tomorrow (saturday) i will have more details abt the car and its problem

thanks once again!

[Jrs3800]

Is the check engine light on? If so it would be adviseable to get the codes checked..

Yes the car is OBD 1 compliant..

A good thing would be to hook a scantool to the car and see what the TPS is doing...

Does this car backfire when you drive it? Miss or stumble maybe even stall out?

Does the car start right away?

Has this been an issue for any length of time or was it a sudden problem? And how many miles do you have on the car?

[gbic1]

I have a 90 lesabre doing same thing. Did you fix this car? with what?

[rbrtdun]

Originally Posted by Jrs3800

Is the check engine light on? If so it would be adviseable to get the codes checked..

Yes the car is OBD 1 compliant..

A good thing would be to hook a scantool to the car and see what the TPS is doing...

Does this car backfire when you drive it? Miss or stumble maybe even stall out?

Does the car start right away?

Has this been an issue for any length of time or was it a sudden problem? And how many miles do you have on the car?

I also have a 1990 Bonneville that sometimes stalls in hot weather. Also it is very difficult to start in hot weather even if it has been sitting all day. My wife uses this car to drive 12 miles to work and after sitting in the sun all day at 90 degrees, it takes 4 or 5 tries to get it started. Then it will jerk and sometimes die in traffic. I have replaced fuel pump & lines, ignition module and coil, etc. Any suggestions?